Supporting structure for engine timing chain

ABSTRACT

A supporting structure for an engine timing chain comprising a chain guide for artificially limiting vertical movement of the timing chain near a camshaft sprocket, thereby reducing any abnormal engagement between the timing chain and camshaft sprocket while the camshaft sprocket is in motion, decreasing noise, and increasing the life of the components.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of Korean Application No.10-2003-0022621, filed on Apr. 10, 2003, the disclosure of which isincorporated fully herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a supporting structure for anengine timing chain and, more particularly, to a chain guide for guidingmovement of a timing chain.

BACKGROUND OF THE INVENTION

[0003] In general, the interaction between a crankshaft and a camshaftthat allows an intake and exhaust valve of an engine to open and closeperiodically causes the driving force to vary periodically because thedriving force transmitted from the crankshaft to the camshaft ismaximized when a cam lobe of the camshaft pushes against the intake orexhaust valve. In an engine using a timing chain around a crankshaftsprocket and a camshaft sprocket, a driving torque is periodicallyvaried during a periodic opening and closing of intake and exhaustvalves. The periodic variation of the driving torque forces the timingchain to move vertically (approximately 3-4 mm) in close proximity tothe camshaft sprocket.

[0004] However, a drawback in conventional engines using a timing chainis that vertical movement generated by the timing chain adjacent to thecamshaft sprocket induces an uneven engagement between the sprocket andtiming chain.

[0005] There is another drawback in that operational noise occurs in thecourse of an engagement of the sprocket and timing chain fortransmitting the driving force.

[0006] There is still another drawback in that the chain link pins ofthe timing chain having relatively weak rigidity get damaged due torepetitive uneven engagement, thereby decreasing the life of components.

SUMMARY OF THE INVENTION

[0007] Embodiments of the present invention provide an engine having atiming chain adapted to artificially restrict vertical movement of atiming chain in close proximity to a camshaft sprocket, thereby reducingany abnormal engagement between the camshaft sprocket and timing chain,decreasing noise, and increasing the life of components.

[0008] In one preferred embodiment of the present invention, asupporting structure for an engine timing chain comprises a timing chaininstalled around a crankshaft sprocket and a camshaft sprocket to allowthe camshaft to interact with the crankshaft for periodically openingand closing an intake and an exhaust valve. A chain guide guidesmovements of the timing chain in close proximity to the camshaftsprocket, such that the timing chain is restricted in vertical movement.

[0009] The chain guide preferably further comprises a body part having aguide groove at its rear portion for allowing the timing chain to beinserted therein. A mounting boss part is integrally formed at a lowerportion of the body part for fixing the chain guide.

[0010] The chain guide is further preferably secured at a cam capmounted on a journal part of the cylinder head, wherein the cam cap isintegrally formed for simultaneously fixing the intake and exhaustcamshafts at the journal part of the cylinder head.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For fuller understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

[0012]FIG. 1 is a schematic drawing of a chain guide mounted on anengine timing chain according to an embodiment of the present invention;

[0013] FIGS. 2(a) and (b) respectively illustrate front and rearperspective views of the chain guide of FIG. 1;

[0014]FIG. 3 is a perspective view illustrating a configuration andinstallation state of a cam cap for mounting a chain guide theretoaccording to the embodiment of the present invention; and

[0015]FIGS. 4 and 5 respectively illustrate front and rear perspectiveviews of the cam cap of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0016] A preferred embodiment of the present invention will now bedescribed in detail with reference to the accompanying drawings.

[0017] As shown in FIG. 1, a timing chain 14 is installed around acrankshaft sprocket 10 and a camshaft sprocket 12. A chain guide 16 ismounted adjacent to the camshaft sprocket 12 to restrict any verticalmovement of the timing chain 14.

[0018] In a double overhead cam (DOHC) engine as shown in FIG. 1, thechain guide 16 is preferably installed between an intake camshaftsprocket 12 a and an exhaust camshaft sprocket 12 b.

[0019] With reference to FIGS. 2(a) and (b), the chain guide 16 isformed with a mounting boss part 16 a at its lower portion for fixingthe chain guide 16 to an engine cylinder head or the like. A body part16 b having a guide groove 16 c for fixing and supporting the timingchain 14 is formed at an upper portion of the mounting boss part 16 a.

[0020] The chain guide 16 may be preferably installed at a cam cap 24 asshown in FIG. 3. The cam cap 24 is designed to fix an intake and anexhaust camshaft 20 and 22 at a journal part 18 a of a cylinder head 18.The cam cap 24 is, therefore, installed on the journal part 18 a of thecylinder head 18 in close proximity to the camshaft sprocket 12. Adetailed configuration of the integral cam cap 24 is illustrated inFIGS. 4 and 5, respectively.

[0021] The cam cap 24, as shown in FIGS. 4 and 5, is formed withreceptive grooves 24 a at both ends of the journal part so as to supportthe intake and exhaust camshafts 20 and 22. A mounting boss part 24 b isdisposed at a front center of the cam cap 24 to be correspondinglysecured to the mounting boss part 16 a of the chain guide 16. A cut-outportion 24 c is formed at a rear part of the mounting boss part 24 b ofthe cam cap 24 to reduce the weight of the components.

[0022] The chain guide 16 may be integrally manufactured with the camcap 24.

[0023] The crankshaft sprocket 10 and camshaft sprocket 12 interact witheach other via the timing chain 14 for periodically opening and closingan intake and exhaust valve of an engine. The chain guide 16, forrestricting the vertical movement of the timing chain 14, is installedeither at an adjacent portion of the camshaft sprocket 12 or between theintake camshaft sprocket 12 a and the exhaust camshaft sprocket 12 b,such that vertical movement of the timing chain 14 according to thedriving torque variation periodically generated from the camshaftsprocket 12 can be forcibly restricted.

[0024] If the timing chain 14 is restricted in vertical movement via thechain guide 16, the camshaft sprocket 12 and timing chain 14 uniformlyengage with each other, so that noise emitted during the engagement isreduced. Furthermore, wear and tear on the components due to an unevenengagement is prevented, contributing to an increase in durability ofthe components.

[0025] The cam cap assembled at the journal part 18 a of the cylinderhead 18 thus described for fixing the intake and exhaust camshaft 20 and22 may be replaced by a cam cap 24 which fixes the intake and exhaustcamshaft 20 and 22 at the same time, resulting in a reduction of thenumber of cam caps required during an engine assembly in comparison withthe typical decoupled cam cap, and facilitation of maintaining thecomponents.

[0026] The cam cap 24 used for installing the chain guide 16 is formedwith the cut-out portion 24 c at the rear portion of the mounting bosspart 24 b, thus reducing the weight of the cam cap integrallymanufactured.

[0027] As apparent from the foregoing, there is an advantage in that thesupporting structure of the engine timing chain includes the chain guide16 and the timing chain 14, which transmits power between the crankshaftsprocket 10 and the camshaft sprocket 12, thereby restricting verticalmovement of the timing chain 14 in conjunction with the periodic changeof the driving torque from the camshaft sprocket 12, reducing noisegenerated by an abnormal meshing between the camshaft sprocket 12 andtiming chain 14, and optimizing the life of components.

What is claimed is:
 1. An engine timing chain assembly, comprising: atiming chain installed around a crankshaft sprocket and a camshaftsprocket to allow a camshaft and a crankshaft to interact with eachother for periodically opening and closing intake and exhaust valves;and a chain guide for guiding movement of said timing chain in closeproximity to said camshaft sprocket and for restricting verticalmovement of said timing chain.
 2. The assembly as defined in claim 1,wherein said chain guide is installed between an intake camshaftsprocket and an exhaust camshaft sprocket.
 3. The assembly as defined inclaim 1, wherein said chain guide comprises: a body part having a guidegroove at its rear portion for allowing said timing chain to be insertedtherein; and a mounting boss part integrally formed at a lower portionof said body part for fixing said chain guide.
 4. The assembly asdefined in claim 1, wherein said chain guide is secured at a cam capmounted on a journal part of the cylinder head.
 5. The assembly asdefined in claim 4, wherein said cam cap is integrally formed forsimultaneously fixing an intake camshaft and an exhaust camshaft at saidjournal part of the cylinder head.
 6. The assembly as defined in claim5, wherein said cam cap further comprises: receptive grooves formed atboth ends thereof for supporting the intake and exhaust camshafts; and amounting boss part integrally protruded from a front center of said camcap for securing said chain guide.
 7. The assembly as defined in claim6, wherein a cut-out portion is formed at a rear portion of saidmounting boss part for reducing the weight of the components.
 8. Theassembly as defined in claim 1, wherein said chain guide is integrallyformed to said cam cap mounted at said journal part of the cylinderhead.